Population structure of a widespread bat (Tadarida brasiliensis) in an island system

Dispersal is a driving factor in the creation and maintenance of biodiversity, yet little is known about the effects of habitat variation and geography on dispersal and population connectivity in most mammalian groups. Bats of the family Molossidae are fast‐flying mammals thought to have potentially high dispersal ability, and recent studies have indicated gene flow across hundreds of kilometers in continental North American populations of the Brazilian free‐tailed bat, Tadarida brasiliensis. We examined the population genetics, phylogeography, and morphology of this species in Florida and across islands of The Bahamas, which are part of an island archipelago in the West Indies. Previous studies indicate that bats in the family Phyllostomidae, which are possibly less mobile than members of the family Molossidae, exhibit population structuring across The Bahamas. We hypothesized that T. brasiliensis would show high population connectivity throughout the islands and that T. brasiliensis would show higher connectivity than two species of phyllostomid bats that have been previously examined in The Bahamas. Contrary to our predictions, T. brasiliensis shows high population structure between two groups of islands in The Bahamas, similar to the structure exhibited by one species of phyllostomid bat. Phylogenetic and morphological analyses suggest that this structure may be the result of ancient divergence between two populations of T. brasiliensis that subsequently came into contact in The Bahamas. Our findings additionally suggest that there may be cryptic species within T. brasiliensis in The Bahamas and the West Indies more broadly.     

Reproductive behavior and social organization in the sand tilefish,Malacanthus plumieri

Synopsis Observations on the Caribbean sand tilefish, Malacanthus plumieri, were made during 3 dive trips in the Bahamas (Feb., 1986; July, 1986; Jan., 1987) at depths from 5 to 30 m. Eighteen mating groups contained 1 to 5 females (x = 2.9). Seven male home ranges (encompassing female ranges within mating groups) measured 250 to 700 m². Of 134 paired rises recorded between 1733 and 1925 h EST, 38 had an observed cloud of gametes. Mating times are presented in relation to time of sunset and depth of water. Courtship begins with conspicuous looping behavior of the male as he swims to a female. Close pairing, criss-crossing, and low rises (<1.5 m) often precede a high quivering upward swim (1.5 to 6 m) which culminates in the release of a cloud of gametes at the apex. M. plumieri is compared to the protogynous hermaphroditic razorfishes, Xyrichtys pentadactylus and X. martinicensis, with regard to social organization, size of male home ranges in exposed sandy habitats near coral reefs, sexual size dimorphism, and sex ratio.     

Dry land drowning or rip current survival? Haitians without status in the Bahamas

Recent scholarship contends that collective action emerges when human rights are violated. This article investigates why Haitians without status in the Bahamas have yet to mobilize collectively for basic rights and protections, despite discrimination and exploitation. The article examines two analogies to explain their immobilization. The analogy of dry land drowning utilizes Goffman's Stigma (1963) framework to describe how social prejudice hinders the ability of Haitians without status to act, while the analogy of rip current survival explains how institutional drawbacks pull Haitians without status away from movement activity through a political process analysis. The article contends that both interpretations are inadequate when taken alone and provides suggestions for future research into Bahamian-Haitian relations.     

Influence of climate change and postdelisting management on long‐term population viability of the conservation‐reliant Kirtland's Warbler

Rapid global climate change is resulting in novel abiotic and biotic conditions and interactions. Identifying management strategies that maximize probability of long‐term persistence requires an understanding of the vulnerability of species to environmental changes. We sought to quantify the vulnerability of Kirtland's Warbler (Setophaga kirtlandii), a rare Neotropical migratory songbird that breeds almost exclusively in the Lower Peninsula of Michigan and winters in the Bahamian Archipelago, to projected environmental changes on the breeding and wintering grounds. We developed a population‐level simulation model that incorporates the influence of annual environmental conditions on the breeding and wintering grounds, and parameterized the model using empirical relationships. We simulated independent and additive effects of reduced breeding grounds habitat quantity and quality, and wintering grounds habitat quality, on population viability. Our results indicated the Kirtland's Warbler population is stable under current environmental and management conditions. Reduced breeding grounds habitat quantity resulted in reductions of the stable population size, but did not cause extinction under the scenarios we examined. In contrast, projected large reductions in wintering grounds precipitation caused the population to decline, with risk of extinction magnified when breeding habitat quantity or quality also decreased. Our study indicates that probability of long‐term persistence for Kirtland's Warbler will depend on climate change impacts to wintering grounds habitat quality and contributes to the growing literature documenting the importance of considering the full annual cycle for understanding population dynamics of migratory species.     

The role of modern and fossil cyanobacterial borings in bioerosion and bathymetry

Measurements on modern coral reefs at Lee Stocking Island (Bahamas) illustrate that boring cyanobacteria species make a major contribution to microboring bioerosion rates. Borings attributed to cyanobacteria also occur in fossil environments. Bioerosional studies on Permian and Triassic reefs show similar intensities to those observed on modern equivalents. The importance of borings assigned to cyanobacterial activity is even more apparent in paleobathymetry. Comparison of the bathymétrie ranges known from modern and fossil microborings demonstrates a preference of boring cyanobacteria for shallow marine environments. Furthermore, some traces are linked to distinct portions of the shallow euphotic zone. They significantly contribute to characterize typical microboring assemblages, which are used for paleodepth reconstructions. In contrast to these stenobathic species, one cyanobacterial species turned out to be eurybathic. It has been recorded as deep as the dysphotic zone but may even extend to the aphotic zone.     

Environmental drivers of diurnal visits by transient predatory fishes to Caribbean patch reefs

Video cameras recorded the diurnal visitation rates of transient (large home range) piscivorous fishes to coral patch reefs in The Bahamas and identified 11 species. Visits by bar jack Caranx ruber, mutton snapper Lutjanus analis, yellowtail snapper Ocyurus chrysurus, barracuda Sphyraena barracuda and cero Scomberomorus regalis were sufficiently frequent to correlate with a range of biophysical factors. Patch‐reef visitation rates and fish abundances varied with distance from shore and all species except S. regalis were seen more frequently inshore. This pattern is likely to be caused by factors including close proximity to additional foraging areas in mangroves and on fore‐reefs and higher abundances close to inshore nursery habitats. Visitation rates and abundances of C. ruber, L. analis, O. chrysurus and S. regalis also varied seasonally (spring v. winter), possibly as fishes responded to temperature changes or undertook spawning migrations. The abundance of each transient predator species on the patch reefs generally exhibited limited diurnal variability, but L. analis was seen more frequently towards dusk. This study demonstrates that the distribution of transient predators is correlated spatially and temporally with a range of factors, even within a single lagoon, and these drivers are species specific. Transient predators are considered an important source of mortality shaping reef‐fish assemblages and their abundance, in combination with the biomass of resident predators, was negatively correlated with the density of prey fishes. Furthermore, transient predators are often targeted by fishers and understanding how they utilize seascapes is critical for protecting them within reserves.     

Long‐term non‐equilibrium dynamics of insular floras: a 17‐year record

Aim To document long‐term rates of immigration, extinction and turnover in insular floras and evaluate the relative impacts of recent hurricane activity and climate change. Location Three archipelagos of small islands, in the Exuma Cays, Andros and Abacos, Bahamas. Methods I surveyed the floras of 194 vegetated islands in three archipelagos over several multi‐year periods, spanning up to 17 years. Changes in abundance (foliar cover) of persistent populations were measured on a subset of 14 islands in the Exuma Cays over a 9‐year period. Results Rates of plant turnover were generally low compared with other organisms, but varied among archipelagos and time periods. Turnover rates were usually higher in the second decade of this study, and extinction rates were often dramatically higher than immigration rates in the second decade, resulting in overall decreases in species richness. Turnover did not differ significantly among island types based on generalized location and surrounding water depths, and extinctions were not more likely to occur on more exposed islands. The abundance (foliar cover) of populations that did not go extinct decreased steadily over the second decade of this study, indicating, along with higher extinction rates, a generalized decline in these insular floras. Main conclusions Although some islands may have been at or near a state of dynamic equilibrium in the first decade of this study, average species richness declined in all three archipelagos during the second decade, when extinctions greatly outnumbered immigrations. Four major hurricanes affected the study archipelagos in the second decade of this study, although the available evidence suggests that the hurricanes were not directly responsible for the declines. Indirect effects of hurricanes such as increased herbivory and possible decreased nutrient availability, along with a long‐term (25 years) increase in temperature and decline in rainfall are likely contributing factors.     

NEW ENDOLITHIC CYANOPHYTES FROM THE NORTH ATLANTIC OCEAN. II. HYELLA GIGAS LUKAS & GOLUBIC SP. NOV. FROM THE FLORIDA CONTINENTAL MARGIN1

A new species of endolithic cyanophyte, Hyella gigas Lukas and Golubic (Order: Pleurocapsales), differs from other species of Hyella by its larger cell and filament dimensions and its laminated, often pigmented sheath. It bores into mollusk shells and other marine carbonate substrates on the east coast of North America, the Bahama Islands and the Northern Mediterranean Sea, where it is found from near mean low water down to 25 m depth. This comparatively shallow maximum depth is probably due to the limited capacity of Hyella gigas to adapt to changing light quality and intensity. We reject the suppression of the genus Hyella as proposed by Drouet and Daily.     

Experimental studies on microbial bioerosion at Lee Stocking Island, Bahamas and One Tree Island, Great Barrier Reef, Australia: implications for paleoecological reconstructions

Different kinds of experimental calcareous substrates were exposed at Lee Stocking Island (Bahamas) and One Tree Island (Great Barrier Reef, Australia) to study which endolithic bacteria, algae and fungi contribute to bioerosion and what their bioerosion rates are. The sites at Lee Stocking Island were several leeward shallow water and several windward shallow and deep-water positions (from the Acropora palmata reef at 2 m down to 275 m depth). At One Tree Island, the experiments were conducted in patch reefs treated with P and N to study the influence of mineral nutrients on bioerosion. The exposure periods ranged from 1 week to 2 years. The micritic carbonate substrates exposed on Lee Stocking Island contained 6 genera with 15 species of cyanobacteria, green and red algae, and different kinds of microendolithic heterotrophs. The mean values of bioerosion rates measured between 1 to 2 g/m²/y at 275 m and 520 g/m²/y at one of the leeward sites. The composition of the endolithic community and the bioerosion rates changed over time. At One Tree Island, shell pieces of Tridacna were used as substrate exposed for 5 months to endolith activity. Five genera and 6 species of cyanobacteria, green and red algae and different kinds of heterotrophic microendoliths were found with bioerosion rates of 20-30 g/m²/y. There are differences in abundance of taxa between Lee Stocking Island and One Tree Island. The introduction of nutrients had no apparent impact on the microborer community. Controlling factors for the distribution and abundance of microborers are mainly light, but also the kind of substrate and, possibly, the biogeographic position. The results support the paleoecological importance of microendoliths.